Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$74.83	9.655%	$82.0548	$82.05	$82.05	$82.10
Purchase #2	$240.87	13.662%	$273.7777	$273.78	$273.80	$273.80
Purchase #3	$11.88	9.649%	$13.0263	$13.03	$13.05	$13.00
Purchase #4	$239.58	9.872%	$263.2313	$263.23	$263.25	$263.20
Purchase #5	$159.80	6.343%	$169.9361	$169.94	$169.95	$169.90
Purchase #6	$134.88	8.741%	$146.6699	$146.67	$146.65	$146.70
Purchase #7	$54.83	8.245%	$59.3507	$59.35	$59.35	$59.40
7 purchase totals =	$916.67		$1,008.0468	$1,008.05	$1,008.10	$1,008.10